Recent years have seen a great increase in the number and diversity of message or information storage systems as more and more people use such systems in business and personal applications. Many such systems, such as E-mail, voice mail, fax, etc., are designed as part of a central office switch in the switched public network, while others are designed to operate in conjunction with a private branch exchange (PBX). In either case, message storage systems typically include one or more voice or data processing units coupled to the switched public network through a finite number of telephone lines. These data processing units are dedicated to serving a group of subscribers, usually employees of the business which owns the PBX. Individual subscribers are usually assigned to a specific processing unit and messages for each subscriber are typically stored in a local storage device connected to the dedicated data processing unit. Normally, groups of data processing units share access to a common storage device.
During periods of heavy usage, the numerous data processing units of a PBX may consume all of the available bandwidth of the common storage device. In such a case, new incoming data for a particular subscriber will not be allowed to be stored because the dedicated processing unit for that subscriber is not able to access the common storage device. Similarly, if a subscriber attempts to retrieve data messages from the common storage device during a period of high usage, the subscriber will be unable to obtain the messages because there is no available bandwidth with which to access the storage device.
Some prior art systems have attempted to avoid the bandwidth limitations of common storage devices by employing a front-end switch which directs incoming calls for a specific subscriber to the dedicated processing unit assigned to that subscriber or, if the dedicated processing unit is busy, to an alternate processing unit. The alternate processing unit will handle the call and store the data messages on an alternate storage device associated with the alternate processing unit.
The data message may then be transferred across an internal network or data bus from the alternate storage device to the dedicated storage device coupled to the dedicated processing unit for that particular subscriber. One such system is disclosed in U.S. Pat. No. 5,029,199, entitled "Distributed Control and Storage for a Large Capacity Messaging System" to Jones et al., which patent is hereby incorporated by reference in the present disclosure.
This solution to the bandwidth limitations of memory storage devices during periods of high traffic in a PBX is nonetheless inadequate. While the prior art messaging systems enable a caller to leave a mail message for a subscriber even if that subscriber's dedicated processing unit is busy, the prior art systems fail to anticipate these situations or attempt to avoid them. Furthermore, if a subscriber calls in to retrieve mail messages and the messages have been distributed to alternate storage devices, the message system must gather the numerous messages from the different storage devices and relay them across the internal network to the processing unit handling the subscriber's message retrieval. This may introduce latencies from several seconds up to a minute or more, depending upon the volume of traffic on the network.
There is therefore a need in the art for a messaging system that distributes utilization across system components thereby avoiding system blockages to individual processors.
There is a further need in the art for a messaging system that, although distributing utilization across system components, consolidates subscribers' messages to decrease latencies experienced in retrieval of a particular subscriber's messages.
There is a still further need in the art for a storage processing system which statistically monitors the frequency and duration of mail messages left by callers for each subscriber and the frequency and duration of mail retrievals by each subscriber for utilization in consolidation of messages.